The present invention is directed to a method and apparatus for processing a color document image. More particularly, the present invention is directed to a method and apparatus for extracting a foreground image and a background image from a color document image.
The popularity of the Internet has led to a dramatic increase in the need to transmit electronic color document images over wide area networks. Because of bandwidth limitations in most networks, the color images typically must be compressed before they are transmitted.
Most known compression techniques are optimized for data with specific attributes. For example, the Joint Bi-level Image Experts Group ("JBIG") compression technique, disclosed in the International Telecommunication Union ("ITU") Recommendation T.82 (1993), places a high emphasis on maintaining the detail and structure of the input. Therefore, JBIG is ideally suited for compressing black & white text and line-art data ("bilevel data"). Similarly, the Joint Photographic Experts Group ("JPEG") compression technique, disclosed in ITU Recommendation T.81 (1993), is ideally suited for compressing color pictures and other color images because it places a high emphasis on maintaining the smoothness and accuracy of the colors.
The Mixed Raster Content Color ITU-T Recommendation T.44 (1997) discloses that it is desirable to decompose a color image into three layers before compressing the image: 1) a bilevel layer of text and line art; 2) a color layer representing the background color of the image; and 3) a color layer representing the foreground color of the image. Each of the layers can then be compressed using the most optimum compression technique and transmitted independently However, ITU recommendation T.44 does not disclose a method or apparatus for extracting the background and foreground layers.
Based on the foregoing, there is a need for a method and apparatus for extracting a foreground image and a background image from a color document image.